Method of splicing thermoplastic monofilaments



y 1950 J. H. LOWER 2,514,184-

IETHOD 0F SPLICING THERMOPLASTIC MONOFILAMENTS Filed June 20, 1946 '7 Sheets-Sheet 1 ENVENTQP;

JAMES H. LOWER ATTORNEYS J. H. LOWER METHOD OF SPLICING THERMOPLASTIC MONOFILAMENTS '7 Sheets-Sheet 2 Filed June 20, 1946 I N v nn-ron JAMES'RIDWEQ AT'TDRNBYS July 4, 1950 J. H. LOWER 2,514,134

WTHOD OF SPLICING THERMOPLASTIC MONOFILAMENTS Filed June 20, 1946 '7 SheetsSheet 25 INVINTOR (JAMES H. LOWER ATTORNEYS Jfiufiy 4, 1950 J. H. LOWER 2,514,134

HETHOD 0F SPLICING THERMOPLASTIC MONOFILAMENTS Filed June 20, 1946 7 Sheets-Sheet 4 eig'aid? ?m4 H 4 I I'\ nuvENTon ATTORNEYS y 9 J. H. LOWER 2,514,184

METHOD OF SPLICING THERMOPLASTIC MONOFILAMENTS Filed June 20, 1946 '7 Sheets-Sheet 5 ,mwu i m a '39 l N V Z NTO R 152 144- v 14. WNW" I39 cJAMES Fr. Lowsm 26 "a A-r-ronuzvs July 4, 1950 J. H. LOWER rm'mon 0F smcmc 'rrmuoPLAs'rzc MONOFILAMENTS 7 Sheets-Sheet 7 Filed June 20, 1946 INVZNTOR -dAME.S H. LOWER ATTORNEYS Patented July 4, 1950 OFFICE" METHOD OF SPLICING THERMOPLASTIC MONOFILAMENTS James 11; Lower, Fairlawn, N. J., assignor to The Firestone Tire 8; Rubber Ohio, a corporation of Ohio Company, Akron,

Application June 20, 1946, Serial No. 677.984

1 Claim. 1

This invention relates to the splicing of organic thermoplastic monofilameuts, and more particularly to the splicing of oriented organic thermoplastic monofilaments such as polyvinylidene chloride and nylon monofilaments.

As stated, this invention relates to the splicing of organic plastic monofilaments, i. e., wire like, solid integral plastic strands of substantial cross section (say -400 circular mils cross sectional area) as distinguished from conventional textile threads composed of a number of very fine filaments held together by twist. In the working up of monofllaments into fabrics, screening, etc. considerable dlfilculty has been encountered-in splicing together lengths of these filaments, as for instance where breaks occur, or where it is desired to make up packages, warps, etc., and the lengths of monofilament at hand are too short for the purpose. Knotting of the mon'ofilaments is highly unsatisfactoryithe mechanical strength of the .knotte'd section is undesirably low; the knots are very prone to come untied during manufacturing operations, articularly in the warp, which is repeatedly fiexed during weaving; and the knots form a particularly objectionable appearance in the final fabric, not encountered witli ordinary multifilament fabrics, due to the relatively incompressible nature of the monofilanrents. Splicing means, other than knotting, have likewise been found unsatisfactory; for instance, it has been conceived that monofilaments might; be spliced together by means of adhesive cements. On account of the smooth, repellent, and non -adhesive character of the monofllament surfaces, however, this procedure was found unsatisfactory.

Accordingly, it is an object of this invention to provide a satisfactory method-for splicing plasticmonofilaments.

Another object is to provide such a method.

which will result in mechanically strong splices between lengths of monofilament.

r A further object is to provide such a method which will result in splices which will withstand repeated flexure in any weaving, etc. operations to which they may be subjected, and which will operate smoothly in any textile working machinery employed.

Still another object is to provide splices which will be inconspicuous in the final woven or other fabrics.

A still further object is to secure the foregoing objects in a process which may be expeditiously carried out by relatively unskilled operators by means of relatively slmpleapparatus.

A still further object is to provide simple and practical apparatus for effecting splices between filaments as above set forth.

I'he above and other objects are secured, in accordance with this invention, by lapping and welding together the ends of the plastic'monofilaments to be joined, the heat for the welding being supplied by subjecting the lapped ends to a high frequency electric field. There result, particularly when conditions areadjusted as more particularly set forth hereinafter, welded joints which approach, in strength,v the continuous portions of the monofilame'hts. The welded joints reliably withstand all usual textile operations and are inconspicuous in theflnal fabric.

The conditions of field frequency, voltage, etc. applied to monofilaments to weld the samein accordance with this invention may be quite widely varied. The primary factor is' thefield frequency, selection of which will approximately determine the values of the other variable condi, tlons to which the monofilaments must be sub- Jected. A field frequency of at least 25 megacycles must be employed. Higher frequencies in the range -250 megacycles, are preferable, as they result in stronger and more reliable welds, and also permit of lower voltages and consequent lessened danger of arcing. Still higher frequencies would be desirable, but in most cases would require excessively elaborate equipment.

The voltage of the field to be applied to the monofilaments to be welded is very difilcult to measure, and if measured, would have little signiflcance apart from the geometry of the specific monofilaments and associated apparatus. For this reason, no more than qualitative instructions can be furnished on this point. In general, the voltage ma be increased or decreased by means available to those skilled in the art. For instance, assuming that a vacuum tube oscillator is' employed for supplying the power, the voltage may be increased by increasing the plate voltage of the oscillator; or by tightening the coupling ,between the plate and grid circuits of the oscillator; or by tightening the coupling between the plate circult and the circuit supplying current to the lapped filaments; or by adjusting the length of power leads to the welding apparatus to coincide with maxima. or less than maxima. of the resonance pattern thereof. The maximum possible voltage will be that at which are discharge of the electric current occurs. Below this maximum voltage, the voltage should be adjusted to a value such as to secure a weld within a certain optimum time, more particularly set forth hereinafter; if, at any particular voltage, the

3 formation of a weld requires a longer period than the optimum, the voltage should be increased; conversely, if a weld is formed in less than the optimum time, the voltage should be decreased.

The time during which the monofilaments are subjected to the electric field is quite critical. In general, the field should not be applied for a longer duration of time than is necessary to effect the weld, as the strength of the weld is deteriorated beyond this point. This duration is an inverse function of voltage and of frequency of applied field; with any selected frequency, the voltage should be adjusted as above described to secure welding in the optimum time for that frequency. These optimum times at various frequencies are:

Table I mqmmmde sigma.

' 50 3 ion 1m 17 250 As above noted, the monofilaments should be held together with a definite pressure during welding, which pressure should preferably be between about 3.0 lb. and about 6.0 lb. per linear inch of monofilament interface to be welded together. Higher and lower pressures may be used, but will result in inferior welds. This optimum pressure does not vary significantly with customary sizes of monofilaments.

A wide variety of thermoplastic monofilaments may be spliced together by means of the process of this invention, the principal criterion being that the material of which the monofilament is made shall be sufficiently thermoplastic so that monofilaments thereof will heat seal, 1. e., will,

adhere to one another when heated and pressed together. Suitable monofilaments will thus be seen to include, for instance, the oriented-crystalline monofilaments produced from polymers of vinylidene chloride and copolymers thereof with minor proportions of other unsaturated compounds copolymerizable therewith such as vinyl chloride, vinyl acetate, vinyl ethers, styrene, acrylic esters and nitriles, etc., examples of commercial products of this type being Velon or Saran products respectively of The Firestone Tire & Rubber Company and of The Dow Chemical Company. Another important class of ther moplastic monofilaments which may be spliced in accordance with this invention are the nylon monofilaments, which are oriented-crystalline high molecular polyamides such as condensation products of hexamethylene diamine with adipic acid, or condensates of -amino caproic acid, etc. Other monofilaments suitable for use in this invention include those comprising polymers of vinyl chloride and copolymers thereof with minor proportions of other unsaturated compounds copolymerizable therewith, such as vinyl acetate,

vinylidene chloride, acrylic esters and nitriles,

styrene, vinyl ethers and the like, an example of this type of fiber being marketed under the name of Vinyon by the Carbide and Carbon Chemicals Corporation; or cellulose derivatives such as cellulose acetate, ethyl cellulose, .benzyl cellulose, etc. By the term monofilament it is intended to designate any wire-like, solid integral plastic strands of substantial cross sectional area (say 25400 circular mils cross sectional area) as distinguished from conventional textile threads composed of a number of very fine filaments held together by virtue of their twist. By the term "monofilament it is also intended to include conventional textile threads which have been impregnated and coated with plastic composition so as to provide a substantially solid monofilament of plastic composition reinforced by the fine filaments of the textile thread, an example of such a product being Textr'on a plasticcoated thread manufactured by the Freydberg Brothers-Strauss, Inc. I

As above briefly noted, a considerable difilculty arises in the practice of. this invention by virtue of the tendency of the electric currents to are around the filaments, especially along the surfaces of any insulating materials used to support the monofilaments in welding position. Such arcing quickly destroys the insulating materials. Thus trouble may be minimized by keeping the surfaces of the insulating materials scrupulously clean. A more effective method, somewhat at variance with the foregoing recommendation for cleanliness, is tolightly coat the surfaces of the insulators with an oil, preferably of the paraflin type. Apparatus s0 coated has operated for days in an entirely satisfactory manner, while identical apparatus, operating under the same conditions without the oil coating, was destroyed in a few hours. The reasons for this phenomenon are obscure, and it is tentatively suggested that the oil film provides a more uniform and less abrupt electrical gradient through the surface of the insulation material. This technique is particularly satisfactory with ceramic insulating materials such as glass, porcelain, alumina and the like.

With the foregoing general discussion in mind, there will now be described specific forms of apparatus for carrying out the process of this invention. The apparatus is shown in the accompanying drawings in which:

Fig. 1 shows a perspective view of a press assembly arranged to weld plastic monofilaments according to this invention.

Fig. 2 shows an enlarged view of the spliced filaments before trimming.

Fig. 3 shows an enlarged view of the spliced filaments after trimming.

Fig. 4 shows an enlarged side view of the electrode assemblies in open position, together with the mode of inserting the monofilaments to be spliced.

Fig. 5 is an enlarged section on the line 5-5 of Fig. 4.

Fig. 6 is a section on the line 6-6 of Fig. 4.

Fig. 7 is an enlarged portion of Fig. 6, with the electrodes in closed position.

Fig. 8 is a wiring diagram of a high frequencygenerator for use in this invention.

Figs. 9 and 10 show an alternative electrode assembly.

Figs. 11-14 show an electrode assembly similar to that of Fig. 4, together with means for automatically trimming the filaments after welding: in these fi ures.

Fig. 11 is a front view of the lower electrode assembly similar to that of Fig. 4, with means for trimming the spliced filaments.

Fig. 12 is a top view of the assembly of Fig. 11.

Figs. 13 and 14 are respectively side and end views of cutting chisels used in Figs. 11 and 12.

Fig. 15 is an enlarged fragmentary top view of a warp of monofilaments spliced in accordance with this invention, together with the adjacent portion of the fabric into which the warp is being woven, and including a portion of the reed of the loom employed in the weaving.

Fig. 16 is a vertical section along the line lO-IO of Fig. 15.

Synopsis of entire apparatus, Figs. 1-8

are allowed to extend beyond the welding apparatus. The movable upper jaw 30 of the press carries an upper electrode assembly 32 and is so arranged that, when the pedal 34 is depressed, the upper Jaw 30 descends and carries the upper electrode assembly 32 down into mating engage- ,ment with the lower electrode assembly 24. A

high frequency electric current from the vacuum tube oscillator 36 is then passed from the upper to the lower electrode assemblies through the lapped monofllaments 23 and 23, causing them to become heated and welded together along the zone 37 as shown in Fig. 2.

It will be noted (Fig. 2) the spliced monofllaments have excess ends 23, 23 since it is inconvenient, in practice, to insert the monofilaments so that their ends do not extend beyond the electrodes. These loose ends maybe snipped oil as indicated in Fig.3 by means of scissors or by special cutters, more particularly described hereinbelow in connection with Fig. 11.

Figs. and 16 illustrate the desirable ieatures, both in the process of weaving, and in the finished fabric, of monoiilamenw spliced together in accordance with this invention. In these figures there is shown a portion 01' a warp oi monoa filaments 39 passing through the dents 43 of the reed of a loom (not shown) on which the warp 39 is "being woven into a fabric 45. Certain of the monofllaments contain welded splices 41, 43 identical with that shown in Fig. 3. It will be seen that the splice 47 passes very smoothly between the dents 43, whereas a knot would be repeatedly abraded and disturbed by the reciprocationoi the dents 43. In practice, it has been found that knots so situated frequently come untiedywith consequent interruption to production. Likewise, it will be seen that the spliced portion 48 disturbs the continuity oi the fabric 45 very little, whereas a conventional knot would be most unsightly.

The lower electrode assembly 24 This assembly is more particularly shown in Figs. 4-7 as comprising a sheet metal electrode 38 sandwiched between two glass plates 40 ("Pyrex #774, manufactured by the Corning Glass Works) in turn which are grasped between two blocks 42 of insulating material (Melmac #592, manufactured by the American Cyanamid Company) which are held together by filaments 28 and II may be inserted in superposed, lapped relation as shown in Figs. 4-8.

The upper working edge 32 of the electrode is relieved at 54 and 56, sothat the welding current and pressure are applied only along the land portion from 58 to 63. Portions 53 and 60 are rounded to avoid concentration 01' electrical stress.

The electrode also has a lug 62 extending from between the plates for the attachment to a wire 34 connected to the oscillator 36.

The upper electrode assembly 32 The assembly more particularly comprises a sheet metal electrode 66 sandwiched between two glass plates 61 (Pyrex #774) which in turn are grasped between two blocks 88 of insulating material and held together by bolts 69 passing therethrough to nuts 10. The assembly is adjustably clamped to the upper press jaw 30 by means of screws 1! extending through the yoke 12 and into the blocks 88. The lower working edge 73 of the electrode extends downward from between the plates 61, and the upper and lower electrode assemblies 24 and 32 are so aligned that, when the upper press jaw 30 moves downwardly, the working edge 13 enters the slot 4i and compresses the superposed, lapped monofilaments 2'8, 28 together and against the land portion from 58 to of the lower elect-rode 3B. This is shown in dashed outline in Fig. 4, and also in full lines in Fig. 7.

Complementarily to the lower electrode 38, the working edge 73 of the electrode 66 i relieved at 14 and 16, so that only the intermediate land portion from 78 to 80 engages the filament; this land portion 18, '80 of the upper electrode is disposed opposite the land portion 58, B0 of the lower electrode as shownin Figs. 4, 6 and 7 so that the welding pressure and current are confined to the weld zone 31. Similarly to the lower electrode 38, the upper electrode is rounded at 18 and 80, and has a lug 82 extending from between the blocks 58 for connection to a wire 84 leading to the oscillator 26.

Kick press mechanism 20 Any conventional press mechanism may be used which will move the upperelectrode assembly 32 into engagement with the lower electrode assembly 24. However since, as will appear from data hereinafter detailed, best results are obtained when the pressure of the electrodes upon the filaments is precisely regulated, the kick press mechanism should preferably include means for regulating the electrode pressure, regardless of the pressure exerted by the operator upon the pedal 34. In the specific mechanism'shown, the press comprises a master arm 84 pivoted to the press standard 86 at '88 and connected by positive mechanical linkage 81 to the pedal 34 so that depressing the latter will positively rock the master arm 84 in counter clockwise sense in the drawing upon its pivot 88. The upper jaw 30 of the press is freely pivoted at 90 upon the standard 86, and a spring buffer 8! is interposed between the upper jaw and the master arm 84, so that the latter, when depressed by actuation oi. the pedal 34, thrusts the upper jaw 30 and electrode assembly 34 carried thereby downward into mat-ing engagement with the lower electrode assembly 24. The

limit of travel of the master arm 84 is set so as not to completely compress the spring buifer 9|, so that the maximum pressure exerted by the electrodes upon the monofilaments will be govemed solely b the tension of the spring buffer,

regardless oi the pressure exerted by the operator upon the pedal 34. y

A slotted-link lost motion connection 02 is provided between the master arm 04 and th upper jaw 80, whereby the ,clockwise rocking oi the master arm is permitted to compress the buffer 9|,

but when the master arm rocks counter-clockwise again, the lost motion is taken up, and the upper jaw and electrode assembly are retracted from the lower jaw and electrod assembly, permitting removal of the welded filaments.

The oscillator 36 Any vacuum tube oscillator may used which is capable of generating currents of frequencies on the order of 25-250 megacycles, and of power requisite (usually drawing about 100-1000 watts plate power input) to efl'ect a weld within the desired time. A suitable oscillator is shown in Fig. 8 as comprising a supply line 04 providing alternating current power: a full wave rectifier drawing its plate power from the line through a self-resetting timing switch 90 and a limit switch I00 placed on the floor I02 beneath the pedal 34 so as to close circuit when the pedal is depressed. The filaments of the tubes in the rectifiers are supplied independently of the switches 98, I00 through wires Ill. The rectifier has a rated out+ put at its terminal I06, I01 01' 2000 volts at 300 ma. D. C. In operation, when the operator depresses the pedal 34, it engages the switch I00 at the limit of its travel, thereby supplying plate power to the rectifier so that rectified high voltage becomes available at the output terminals I06 and I 01. The timing switch I00 is arranged to automatically break circuit at the end of the interval for which it is set, and to reclose itself in readiness for the next cycle of operations.

The oscillator proper more particularl includes conducting bridge IIO across the tubes 1 II-which is slidable along the tubes to tune the circuit. The grids of the tubes III are connected together and to the center tap oi the filament transformer I I4 through a leak resistor I I1.

The plate circuit comprises a connection II! from the negative terminal I08 otthe rectifier to the center tap of the filament transformer I II. The plates ofthe tubes I00 are connected to a tank circuit comprising a pair 01' %".O. D. copper tubes I20 12" long spaced 'V apart and provided with a sliding conducting, bridge I22 for tuning. Return to the positive terminal I01 is 3196 radio frequency choke I26 (20 mh.) and wire High frequency power is abstracted from the plate circuit by means of a hair pin loop I32 01 M1" copper tubing, mounted so as to be movable into or out of the field of the tank circuit I20, I22 to increase or decrease the voltage applied to the electrodes 30, 0'.

Optimum conditions of operation A series of welds were made between filaments withthe apparatus of Fig. 1, using various types of plastic mcnofllaments at'various frequencies: various times of welding and correlated applied voltages: and various degrees of pressure on the electrodes as set forth herewith in Table II. From a consideration of the table, it will be apparent that best results are obtained with.

pressures of from about 3.0 lb. to about 6.0 lb. per linear inch (Table II, items Nos. 12-15), and that the optimum times welding follow the scliiedgle of Table I (see Table II, items Nos. 2 an Table II Filament l t em Frequency. Time. Tensile Material Diag e ter, megacycles mud-5 oI mutant) pounds l Saran 15 25 3 4 2. 0

2..- so a 4 as Q 1 4 3. 3 4 5 4 .29 5 6 4 2. a 6-"..- Saran L.-- 15 10 4 2. 2 7 15 4 1. 6

11 Saran 15 175 40 4 4. 0

12...; 2s v 1. a 3.1

a 15 I o. 0 4:3

16.--" Saran L--- 10 175 25 4 2. 1 17.--" Nylon 15 175 25 4 D. U 18.--" T801011 18 175 4 6. 0

I Olive drab Iorm'ulation oi vinylidene chloride resin, oriented after extrusion. 1 Unpigmented nylon filament, oriented after extrusion. I Plastic coated filaments manufactured by Freydberg Erna-Strauss Inc.

two T-40 tubes I00, having a filament-grid tuning circuit comprising two 0. D. copper tubes H0, 12'' long and spaced apart, connected to one end of the filaments of the tubes by wires I I2. The filaments are heated by current derived from the transformer I I4 through insulated wires II! threaded through the copper tubes H0 and connected to those ends of the filaments of the Modified electrode assembly (Figs. 9 m 10) A modified form of the welding electrode ar-' rangement is shown in Figs. 9 and 10 as comprising identical upper and lower electrode assemblies I36, I38 secured respectively to the upper and lower jaws 30, 22 of the kick press 20. Each electrode assembly comprises a sheet metalelectubes III to 'whichthe copper tubes IIO are not trode I31 sandwiched between a pair of blocks I33 of insulating material, which blocks are com- .pressed together by means of a screw I43 passing therethrough into nuts I. Each electrode assembly is secured to its corresponding press jaw by means of screws I42 passing through yokes I43 and into the insulating blocks I35.

' of the jaws of the press, the monofllaments, I3, 23

cradled in the grooves I48 are pressed together in overlappingrelation. A high frequency current is then passed between the electrodes I36, effecting a weld of the monofllaments.

Various means may be employed for inserting and retaining the monoiilaments in the grooves I46. One simple means comprises a pair of notches, II and' I52 cut out of each end of the electrode assembly with their apexes coinciding with the groove I48. A pair of spring clips I53 are secured to the assembly by the screws I43 and have ears I54, I56 yieldably embracing the ends of the electrode assembly. In use, to insert a monofilament such as 26 into the groove in cradled position, one end of the filament is slipped under the ear I54; the filament is drawn, over the notch I50; over the groove I43; down into the notch I5I; and under the ear I56. The filament is held taut during these operations, so

that the notches I50, I5I guide the filament into the groove I48. The spring ears I54, I56 hold the filaments taut in the groove I43 during the welding operations.

Trimming knife assembly Figs. 11-15 show a lower electrode assembly similar to the electrode assembly 24 of Figs. 1-6 and designed to replace the same, and being provided with means for cutting off the excess ends 323, 325 of the monoiilaments 326, 323 after the conclusion of the welding operation. The assembly more particularly comprises a sheet metal electrode 338, glass plates 340, and insulating blocks 342 all similarly constructed and arranged upon the lower jaw 22 of the press as are the corresponding elements 38, and 42 of Fig. 4. (To indicate parts in Figs. 11-14 corresponding to those in Figs. l-6, the reference characters in Figs. 1-6 have been increased by 300; thus 38 in Fig. 4 is the same element as 333 in Fig. 13, and so on.) The insulating blocks 342 are of considerable width and have slideways 444 pierced therethrough, in which chisels 443 and 441 reciprocate for the purpose of cutting oi! the excess ends 323, 325 of the monofllaments.

The chisel 446 comprises a horizontally directed dividing portion 448 and an upwardly directed cutting portion 450, its edge being aligned with the end 452 of the welded zone of the filament. The forward end of the dividing portion 448 is ground off to provide a slanting separating blade 454 extending between the monoillament 328 and the excess end 323. The function of this separating portion is to pry the monofilament and excess end apart as the knife 446 is pushed toward the monofilaments. The forward end of the cutting portion 450 is ground to a cutting edge 456. In operation; assuming that a weld has just been completed between the monofilaments, the chisel 446 is pushed in its slideway, toward the monofllaments. The. separating blade 454 enters between the monoiilaments and forces them apart. Continued motion of the chisel brings the cutting edge 456 into engagement with that portion of the loose end 323 immediately adjacent the welded zone 331 whereby the loose end 323 is clipped oil.

The rear portion 453 of the chisel is square in cross section,. and the corresponding rear portion of the siideway 444 is likewise square in cross section and snugly embraces the square portion 453 of the chisel, so as to permit the chisel to be reciprocated longitudinally while preventing rotation thereof about its longitudinal axis-which rotation, if not restrained, would spoil the register of the chisel with the filaments. The forward end of the slideway 444 is enlarged to form a pocket 460 into which the chisel is withdrawn when not in action. The blades 448, 450 abut the rear walls of the pocket 463 so as to limit the retraction of the chisel. The exterior end of the chisel provided with a knob 462, which may be pressed to actuate the chisel to trim ofl the excess end 323. A helical compression spring 464 surrounds the chisel between the knob 462 and the block 342 to retract the chisel after such actuation'.

The chisel 441 is arranged and constructed identically to the chisel 446, but is positioned to cut ofl theloose end 325. The knives 346 and 341 are shown as being provided with knobs 462, whereby they maybe manually reciprocated to effect the cutting action. However, pneumatic or electrical means may be provided to effect this movement'automatically upon the conclusion of the welding operation.

From a consideration of the foregoing description, it will be seen that this invention provides a novel method and apparatus for effecting splices between thermoplastic. monofilaments. The apparatus and procedure involved are simple and inexpensive, and the welded filaments are strongly and permanently united.

What is claimed is:

Process which comprises overlapping, in parallel relationship, the ends of two lengths of thermoplastic monofilament, confining said overlapped monofilaments between two parallel walls of ceramic insulating material, the surfaces oi the walls adjacent the monofllaments being coated with oil, compressing said monofllaments together within the space between said walls by means of metallic electrodes, with a force of from about 3.0 to about 6.0 pounds per linear inch of overlapped monofilaments, and supplying to the electrodes an alternating potential having a frequency of from about to about 250 megacycles and of voltage such that a weld is effected between the filaments within a period of time which is a function of the frequency employed, substantially in accordance with the table:

JAMES H. LOWER.

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